How to unlock the subdivision settings
The green color (and the yellow on Optimal Display) indicates you've set keyframes for those values. Right-click on them and choose &quot;Clear Keyframes&quot;.
Green color means, there are keyframes for this value but not on the frame you're currently on. The yellow color means, there is a keyframe right on this frame.
When you are on a yellow-colored value, right-clicking also gives the option to &quot;Delete Keyframes&quot;. If you do this, only the keyframe on this frame will be deleted and others (if there are any) will stay, so the color will switch to green.
If you want to completely get rid of them (because it seems you've set them accidentally), then &quot;Clear Keyframes&quot; is what you want to  do.